Methods and devices for the analyte detection and concentration measurement in a fluid sample are well known. For example, various devices and methods are known for determining glucose, ketone bodies, cholesterol, lipoproteins, triglycerides, acetaminophen or HbA1c concentrations in a sample of a bodily fluid such as urine, blood, plasma or interstitial fluid. Such determinations can be achieved using analytical test strips, based on, for example, visual, photometric or electrochemical techniques.
In an electrochemical technique, a fluid sample is placed into a sample chamber of an electrochemical cell of a sensor that includes at least a counter and working electrode. The analyte reacts with a redox reagent in the cell to form an oxidizable or reducible substance. The quantity of oxidizable or reducible substance may be electrochemically determined and related to the amount of the analyte present in the sample.
In the case of the measurement of glucose in a blood sample, the measurement may be based on the selective oxidation of glucose by means of an enzyme. For example, the enzyme glucose oxidase catalyzes the oxidation of glucose to gluconic acid by transfer of electrons from the glucose molecule to a prosthetic group embedded within the enzyme structure. This prosthetic group, now in a reduced state may be re-oxidized by addition of a suitable mediator which in turn assumes a reduced state. Conducting these reactions within an electrochemical cell with a test voltage applied between two electrodes creates an output current by the electrochemical re-oxidation of the reduced mediator at the electrode surface. In an ideal environment, stoichiometric principles dictate that the amount of reduced mediator created during the enzymatic reaction is directly proportional to the amount of glucose present in the sample. Therefore, the test current generated is directly proportional to the concentration of glucose in the sample. The current generated may be detected by an analyte measurement device, such as a test meter, used in conjunction with the electrochemical cell or test strip and converted into a glucose concentration reading using an algorithm that relates the test current to a glucose concentration via a simple, mathematical relationship. Conventional electrochemical-based analytical test strips are described in, for example, U.S. Pat. Nos. 6,179,979, 6,193,873, 6,284,125, 6,716,577, 6,749,887, 6,797,150, 6,863,801, 6,872,298, 7,045,046, 7,498,132, 7,846,312, 6,413,410 and 7,749,371 each of which is hereby incorporated in its entirety by reference.
Sensors for use in analyte testing, in which electrochemical cells are incorporated, typically use a carrier material to provide structural integrity and facilitate handling. The carrier materials may take any form, but typically are in the form of a test strip. The costs of sensor manufacture are related to the materials used and certain cost benefits accrue from reducing the quantities of specialized materials used in constructing the test strips, such as by using specialized materials in constructing only the electrochemical cell. However, manipulation of sensors that primarily constitute an electrochemical cell present challenges to end-users due to the resulting reduced size. Additionally, a small-sized strip or sensor increases the potential for contaminating the port of the meter, into which the sensor is placed, with the fluid being analyzed. Therefore, it is desirable for purposes of cost and manipulation to construct sensors having a reduced dimension wherein only the electrochemical cell component is made from specialized materials.